When completing a well, production zones are provided by submerging a casing string having annular barriers into the borehole of the well. When the casing string is in the right position in the borehole, the annular barriers are expanded or inflated. The annular barriers are in some completions expanded by pressurised fluid, which demands a certain amount of additional energy in order to pressurise the well tubular structure to a pressure sufficient to expand a metal sleeve of the annular barrier.